Traditional task killers only kill the running apps, which cause them to leave behind garbage data in RAM memory which then has to be cleared by the system, even on later versions of Android such as Kitkat 4.4. Speed Boost Pro is different because it cleans cache and leftover RAM data from your device in one simple button.

Notes for AutoClean feature:

By default, AutoClean is disabled, but can be changed through settings.

File System optimizations can be opted to be ran with the AutoClean, but must be enabled through settings, accessible through Menu>AutoClean Frequency>File System Optimization.